Network operators are becoming more and more interested in offering Ethernet services, such as Ethernet Private Line services. They offer transparent transfer of Ethernet frames in point-to-point Ethernet connections. Ethernet LAN services are becoming popular as well. They offer multipoint-to-multipoint services.
In general, a network architecture 100 for offering these Ethernet services is shown in FIG. 1. The Ethernet providers network 102 is shown as a cloud with some edge bridges 104 having network ports 105. Customer LANs 106 having customer ports 107 are connected to the network ports 105 of the edge bridges 104.
Frames from customer LANs 106 entering the Ethernet providers network 102 via an edge bridge 104 are classified into a single Service Instance (either a line or a LAN service). Frames belonging to a certain Service Instances may only leave the network via edge bridge ports 105 that are connected to the customer LANs' port 107 of that Service Instance.
The provider can choose between at least the following two methods to provide the Ethernet services: 1) using an IEEE 802.1 bridged network, or 2) using an IETF VPLS network. There are several other techniques that provide this service. Embodiments of the present invention are described herein using only the above two methods but it should be understood that the present invention is not limited to these two techniques.
In the IEEE 802.1 bridged network case, as shown in a network architecture 200 of FIG. 2, the providers network 202 is a bridged LAN as defined in the appropriate IEEE 802 standards (IEEE 802.1D-2004, IEEE 802.1Q-2003, IEEE 802.1 ad-draft 1-4), incorporated by reference herein in their entirety. The active topology is limited to form a spanning tree. All nodes are connected, but between every pair of nodes, there is just one path possible. That is, the topology is loop-free. If there are the potential for loops, ports or links are blocked or removed.
For example, a packet may go from edge bridge 204C to edge bridge 204B via internal bridge 204D to edge bridge 204A and then to edge bridge 204B. But the packet may never go from edge bridge 204A to edge bridge 204C via edge bridge 204B because port 208 of the internal bridge 204D is blocked. Only the direct transfer from edge bridge 204A to edge bridge 204B is allowed according to IEEE 802 standards and protocols.
This path may cross other edge bridges, i.e., these edge bridges forward frames based on the Ethernet MAC addresses and VLAN ID. VLAN ID's are used to separate frames belonging to different Service Instances. For example, the path between edge bridge 204C and edge bridge 204B contains edge bridge 204A and internal bridge 204D. Therefore, all frames from edge bridge 204C to edge bridge 204B, and vice versa, are switched by all edge bridges 204A, 204B, 204C and internal bridge 204D.
Several disadvantages exist with the IEEE 802.1 technique. One is to loose certain paths because of some disabled links. Another is the complexity of the protocol used to achieve this configuration. Finally, there may be a slow recovery time of the protocol.
In the IETF VPLS network case, on the other hand, as shown in FIG. 3, there are only edge bridges 304A, 304B and 304C, with no internal bridge 304D. Every edge bridge has a direct connection to every other edge bridge, i.e., only the edge bridges forward frames based on the Ethernet MAC address. There may be nodes between the edge bridges, but there is no need to switch based on MAC address in these nodes. MPLS labels are used to separate frames belonging to different Service Instances on the links between the edge bridges. If there is a call for an IP packet from 304A to 304C, it will never go via 304B. Only the direct transfer between two edges is allowed under this protocol. An IP packet to go from 304A to 304B to 304C is not allowed.
The main difference between the two approaches discussed above and shown in FIG. 2 and FIG. 3 is that the IETF VPLS network approach has a direct link between every pair of edge bridges and in this approach only the edge bridge forwards based on the Ethernet MAC address.
Both methods have advantages and disadvantages. The IEEE 802.1 bridge LAN method is very efficient if there is a lot of multicast traffic within a Service Instance because only one copy of the multicast frame has to be sent over the spanning tree, whereas, in the IETF VPLS network scenario, this frame has to be replicated and sent separately for each destination.
The IETF VPLS network method allows for efficient traffic engineering. Every edge bridge is directly connected to every other edge bridge in the network. Edge bridges can only forward inside the network to customer or from customer toward an edge bridge. But, they never forward or receive from one edge bridge to another edge bridge. If a customer desires a multipoint service and knows the traffic matrix between the endpoints, the operator can easily configure the required amount of capacity between each endpoint, and force the customer not to exceed this amount. In an IEEE 802.1 bridged LAN network, in general, this is not possible.
Thus, both methods, i.e., IEEE 802.1 bridged LAN and IETF VPLS network, have their own advantages. Heretofore, however, it was not possible to apply the IETF VPLS method using hardware developed for IEEE 802.1 bridged LAN network compliant bridges.
Thus, there is a need in the art for a method to configure an existing compliant bridge network so it can behave according to the IETF VPLS network.